@beckyt despite the not-so-positive reviews from others users in this discussion, I actually love the Geopress. I bought mine about a month ago and have already used it on 2 backpacking trips (a 3-day trip and a 4-day trip) in the U.S. I use the 24 oz Geopress.
Some people may say that the likelihood of finding viruses in U.S. water sources is low, they have been known to exist, and it's always better to be safe than sorry! The safest bet is to get a water filter/purifier that not only removes/kills water-born pathogens (viruses, bacteria, protozoa, etc.), but also sediments, dissolved organics, chemicals, pesticides, and metals (You never know what could be in the water you are drinking!). The Geopress does all of this.
Moreover, I actually find the Geopress to purify water quite quickly and easily (it's not hard to compress at all). I have only used one purifier cartridge so far (although I brought a second one with me on the trip just in case, as this was my first time using the product and was traveling in an area where the water has a lot of sediment and tannins), have already used it 37 times, and find that the filter still works great.
Additionally, each purifier cartridge is rated to work for approximately 250 L (350 cycles/uses), which is a lot of water, especially if you are trying to filter for numerous people, as I was. One thing to keep in mind is that the amount of sediment/dissolved organics in your water sources will affect how many uses any single water filter/purifier will give you. This is why I recommend you always bring a back-up cartridge/filter, no matter what system you are using!
The Geopress is also cheaper than a lot of other purifiers, although it is not cheap, but it's definitely a bang for your buck! You are paying for quality. Moreover, if you are purifying water for numerous people, this is a very inexpensive method! Each cartridge costs $30, which initially seems a bit expensive, but when you calculate how much water ends up costing per gallon using the Geopress, it's actually quite cheap! $0.46 / gallon, to be exact! (One cartridge purifies 65 gallons and costs $30. By dividing 30 by 65, we get the cost of water/gallon via the cartridge, which = $0.46). This is even cheaper than buying a gallon of water from the grocery store!
While it is a bit heavy, I do not find this weight to be significant enough to worry about. Besides, it carabiners great to the outside of your pack if you are short on space! Grayl also makes an ultralight version of this purifier if you are concerned about the weight.
The design of the bottle also makes water contamination extremely unlikely. You can also store filtered water inside the bottle if you want to maximize the amount of water you are carrying!
I also love the texture of the outside of the bottle - it is so grippy that even when your hands and it are wet, you won't drop it/it doesn't slip!
I plan to use the Geopress when I travel internationally as well, but personally I find it to be a great water purifier option for backpacking in the U.S. I have used several other filters in the past, but would rank this one above all others that I have used.
Lastly, another awesome thing is that Grayl has a recycling program for the Geopress purifier cartridges, so you can reduce your carbon footprint!
one or more gifts or other benefits from the co-op.